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• LINQ to SQL Web Application Best Practices

  - by derek

  In my experience building web applications, I've always used a n-tier approach. A DAL that gets data from the db and populates the objects, and BLL that gets objects from the DAL and performs any business logic required on them, and the website that gets it's display data from the BLL. I've recently started learning LINQ, and most of the examples show the queries occurring right from the Web Application code-behinds(it's possible that I've only seen overly simplified examples). In the n-tier architectures, this was always seen as a big no-no. I'm a bit unsure of how to architect a new Web Application. I've been using the Server Explorer and dbml designer in VS2008 to create the dbml and object relationships. It seems a little unclear to me if the dbml would be considered the DAL layer, if the website should call methods within a BLL, which then would do the LINQ queries, etc. What are some general architecture best practices, or approaches to creating a Web Application solution using LINQ to SQL?

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• SImplifying with LINQ - Basic selection

  - by baron

  Hello foreach (var person in peopleList.Where(person => person.FirstName == "Messi")) { selectPeople.Add(person); } I am just wondering if there is any way to simplify this using LINQ. Like rather than look at all the people I was trying to use LINQ to just fill a list with the "Messi"'s... was trying something like... var selectPeople = peopleList.Select(x=>x.FirstName=="Messi"); Then I could just add everyone in that list without a check. But it doesn't quite work as planned. Maybe there's no point simplifying that expression. But the question seemed worthwhile just to strengthen my LINQ knowledge.

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• Deleting objects through foreign key relationship with T-SQL query

  - by LaserBeak

  Looking for a way to write the following LinQ to entities query as a T-SQL statement. repository.ProductShells.Where(x => x.ShellMembers.Any(sm => sm.ProductID == pid)).ToList().ForEach(x => repository.ProductShells.Remove(x)); The below is obviously not correct but I need it to delete respective ProductShell object where any ShellMember contains a ProductID equal to the passed in variable pid. I would presume this would involve a join statement to get the relevant ShellMembers. repository.Database.ExecuteSqlCommand("FROM Shellmembers WHERE ProductID={0} DELETE FK_ProductShell", pid); I have cascade delete enabled for the FK_ShellMembers_ProductShells foreign key, so when I delete the ProductShell it will delete all the ShellMembers that are associated with it. I am going to pass this statement to System.Data.Entity Database.ExecuteSqlCommand method.

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• Performance concern when using LINQ "everywhere"?

  - by stiank81

  After upgrading to ReSharper5 it gives me even more useful tips on code improvements. One I see everywhere now is a tip to replace foreach-statements with LINQ queries. Take this example: private Ninja FindNinjaById(int ninjaId) { foreach (var ninja in Ninjas) { if (ninja.Id == ninjaId) return ninja; } return null; } This is suggested replaced with the following using LINQ: private Ninja FindNinjaById(int ninjaId) { return Ninjas.FirstOrDefault(ninja => ninja.Id == ninjaId); } This looks all fine, and I'm sure it's no problem regarding performance to replace this one foreach. But is it something I should do in general? Or might I run into performance problems with all these LINQ queries everywhere?

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• Linq to NHibernate using Queryable.Where predicate

  - by Groo

  I am querying an SQLite database using LINQ to NHibernate. Person is an entity containing an Id and a Name: public class Person { public Guid Id { get; private set; } public string Name { get; private set; } } Let's say my db table contains a single person whose name is "John". This test works as expected: var query = from item in session.Linq<Person>() where (item.Name == "Mike") select item; // no such entity should exist Assert.IsFalse(query.Any()); but this one fails: var query = from item in session.Linq<Person>() select item; query.Where(item => item.Name == "Mike"); // following line actually returns the // "John" entry Assert.IsFalse(query.Any()); What am I missing?

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• EF 6 Code First Many to many With Payload and self referencing many to many

  - by lesley86

  I Have the problem where i have a many to many relationship and on one of the tables there will be a self referencing many to many. So basically a school have zero or many groups and many groups can have 0 or many schools. The groups table will contain a parent child many to many with itself because a group can be a child of another group or it can have no children and that child can have a child, one child can also have many parents or a entity can have no parents. I created a mapping table with Payload to solvethe first many to many problem. code snippet public class School { public virtual ICollection<SchoolGroupMap> SchoolGroupMaps } public class SchoolGroup { public virtual ICollection<SchoolGroupMap> SchoolGroupMaps } public class SchoolGroupMap { public virtual School School public virtual SchoolGroup SchoolGroup } i Then tried modifying the code the following way for the the self referencing many to many public class SchoolGroup { public virtual ICollection<SchoolGroupMap> SchoolGroupMaps public virtual ICollection<SchoolGroup> Parents public virtual ICollection<SchoolGroup> Children } I changed the context with has many and an auto mapping table (forgive me i have been trying so many things today i do not have the exact code). I received an error the properties on the classes must match. Can anyone help please. I want to do create navigation properties on the self referencing many to many. Also a seed example would be appreciated regards

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• COM+ Connection Pooling Doesn't Appear to be working on SQL Server 2005 Cluster

  - by kmacmahon

  We have a COM+ Data Layer that utilized Connection Pooling. Its deployed to 3 clusters, 2 SQL Server 2000 and 1 SQL Server 2005 environment. We noticed today that our monitoring software is reporting Thousands of Logins per minute on the SQL Server 2005 box. I did some tracing in both environments and profiler is reporting this for the 2000 boxes: sp_reset_connection SQL CALL sp_reset_connection SQL CALL sp_reset_connection SQL CALL and this for the 2005 box: Audit Logout sp_reset_connection Audit Login SQL CALL Audit Logout sp_reset_connection Audit Login SQL CALL Audit Logout sp_reset_connection Audit Login SQL CALL Is there some sort configuration for SQL Server 2005 different from SQL Server 2000 that we might be missing that would be creating this issue?

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• Databinding multiple tables linq query to gridview?

  - by Curtis White

  My question is how can I display a linq query in a gridview that has data from multiple tables AND allow the user to edit some of the fields or delete the data from a single table? I'd like to do this with either a linqdatasource or a linq query. I'm aware I can set the e.Result to the query on the selecting event. I've also been able to build a custom databound control for displaying the linq relations (parent.child). However, I'm not sure how I can make this work with delete? I'm thinking I may need to handle the delete event with custom code.

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• LINQ query needs either ascending or descending in the same query

  - by Sir Psycho

  Is there anyway this code can be refactored? The only difference is the order by part. Idealy I'd like to use a delegate/lamda expression so the code is reusable but I don't know how to conditionally add and remove the query operators OrderBy and OrderByDescending var linq = new NorthwindDataContext(); var query1 = linq.Customers .Where(c => c.ContactName.StartsWith("a")) .SelectMany(cus=>cus.Orders) .OrderBy(ord => ord.OrderDate) .Select(ord => ord.CustomerID); var query2 = linq.Customers .Where(c => c.ContactName.StartsWith("a")) .SelectMany(cus => cus.Orders) .OrderByDescending(ord => ord.OrderDate) .Select(ord => ord.CustomerID);

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• Possible Performance Considerations using Linq to SQL Repositories

  - by Robert Harvey

  I have an ASP.NET MVC application that uses Linq to SQL repositories for all interactions with the database. To deal with data security, I do trimming to filter data to only those items to which the user has access. This occurs in several places: Data in list views Links in a menu bar A treeview on the left hand side containing links to content Role-based security A special security attribute, inheriting from AuthorizeAttribute, that implements content-based authorization on every controller method. Each of these places instantiates a repository, which opens a Linq to Sql DataContext and accesses the database. So, by my count, each request for a page access opens at least six separate Linq to SQL DataContexts. Should I be concerned about this from a performance perspective, and if so, what can be done to mitigate it?

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• Linq ChangeConflictException (ASP.NET MVC) - occurs when submitting DataContext changes

  - by Alex

  System.Data.Linq.ChangeConflictException: 2 of X updates failed. at System.Data.Linq.ChangeProcessor.SubmitChanges(ConflictMode failureMode) at System.Data.Linq.DataContext.SubmitChanges(ConflictMode failureMode) at PROJECT.Controllers.HomeController.ClickProc(Int32 id, String code, String n) This is what I get very often. This action is done thousands of times a day, and I get this exception about once every 5 seconds. From what I understand it happens when something changes in the database in the period between creating DataContext and updating it. Am I right? What's the problem here and how can I fix it?

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• Join Where Rows Don't Exist or Where Criteria Matches...?

  - by Greg

  I'm trying to write a query to tell me which orders have valid promocodes. Promocodes are only valid between certain dates and optionally certain packages. I'm having trouble even explaining how this works (see psudo-ish code below) but basically if there are packages associated with a promocode then the order has to have one of those packages and be within a valid date range otherwise it just has to be in a valid date range. The whole "if PrmoPackage rows exist" thing is really throwing me off and I feel like I should be able to do this without a whole bunch of Unions. (I'm not even sure if that would make it easier at this point...) Anybody have any ideas for the query? if `OrderPromoCode` = `PromoCode` then if `OrderTimestamp` is between `PromoStartTimestamp` and `PromoEndTimestamp` then if `PromoCode` has packages associated with it //yes then if `PackageID` is one of the specified packages //yes code is valid //no invalid //no code is valid Order: OrderID* | OrderTimestamp | PackageID | OrderPromoCode 1 | 1/2/11 | 1 | ABC 2 | 1/3/11 | 2 | ABC 3 | 3/2/11 | 2 | DEF 4 | 4/2/11 | 3 | GHI Promo: PromoCode* | PromoStartTimestamp* | PromoEndTimestamp* ABC | 1/1/11 | 2/1/11 ABC | 3/1/11 | 4/1/11 DEF | 1/1/11 | 1/11/13 GHI | 1/1/11 | 1/11/13 PromoPackage: PromoCode* | PromoStartTimestamp* | PromoEndTimestamp* | PackageID* ABC | 1/1/11 | 2/1/11 | 1 ABC | 1/1/11 | 2/1/11 | 3 GHI | 1/1/11 | 1/11/13 | 1 Desired Result: OrderID | IsPromoCodeValid 1 | 1 2 | 0 3 | 1 4 | 0

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• nHibernate Linq Projection

  - by Craig

  I am using the version 1.0 release of Linq for nHibernate. When I run the following linq statements I receive the error not a single-length projection: Surname I can find very few references to this on the web and looking into the source it says it should never occur! ClientID is a Int type and Surname is a string. When I comment out all the string fields in the projection and just leave ClientID it runs ok, but as soon as I add surname back it errors. var context = m_ClientRepository.Linq; var result = (from client in context from address in client.Addresses from contact in client.Contacts where client.Surname.StartsWith(surname) && client.GivenName.StartsWith(givenName) && contact.Value.StartsWith(phoneNumber) group client by new { client.ClientID, client.Surname, client.GivenName } into clientGroup select new ClientSearchDTO() { ClientID = clientGroup.Key.ClientID, Surname = clientGroup.Key.Surname, GivenName = clientGroup.Key.GivenName, Address = clientGroup.Max(x => x.Addresses.FirstOrDefault().Address), PhoneNumber = clientGroup.Max(x => x.Contacts.FirstOrDefault().Value) }) .Skip(Paging.FirstRecord(pageNumber)) .Take(5);

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• Which data framework is better for an ASP.NET MVC site - LINQ to SQL or NHibernate

  - by Paul Alexander

  We're about to embark on some ASP.NET MVC development and have been using our own entity framework for years. However we need to support more than our entity framework is capable of and so I'd like to get some opinions about using MVC with a more robust framework. We have narrowed down or choices to either NHibernate (with the Fluent APIs) or LINQ to SQL. Which framework lends itself best to MVC style development (I know SO uses LINQ to SQL)? If we want to support SQL Server, Oracle, MySQL - does that exclude LINQ to SQL?

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• LInq to SQL - Partial Class - C#

  - by Mark Comix

  Hi, I have a system with 2 different projects, one is called LINQ_Extensions and the other is ORM_Linq. On ORM_Linq i have the LINQ diagram with the SQL tables "converted" in clases. One of the Class is called "Tipos_Pago" In the other project i have another class (partial class) "Tipos_Pago". I want to use the method OnValidate to validate the properties include in the class "Tipos_Pago", so i create this partial class. In the 2 projects i put the same NameSpace "ORM_Linq"(I changed the NameSpace of the project "LINQ_Extensions" to have the same of the project "ORM_Linq") After those chages, Visual Studio give me this error: Error 1 No defining declaration found for implementing declaration of partial method 'ORM_Linq.Tipos_Pago.OnValidate(System.Data.Linq.ChangeAction)' C..\Tipos_Pago.cs 13 22 Extensiones_Linq I don't have any Idea of what happend, can someone help me? Thanks, sorry for my poor english This is the code in the partial class: namespace ORM_Linq { public partial class Tipos_Pago { partial void OnValidate(System.Data.Linq.ChangeAction action) { //Valid code } } }

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• Get Average Using LINQ

  - by obautista

  Hoping someone can help me with the LINQ syntax to calculate an average. For example, I have the following LINQ query: var rates = from rating in ctx.Rates where rating.Id == Id select new { UserId = rating.UserId, Rating = rating.Rating }; If 10 records are returned, I need to calculate average on the Rating field. It is defined as as a Double in my DB. I am using LINQ to EF. So I would be assigning the UserId, MiscId, and the Rating would be the average on the records returned. I am passing one object back to the client code.

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• C# - LINQ Statements with OR clauses

  - by user70192

  Hello, I am trying to use LINQ to return a list of tasks that are in one of three states. These states are: 10 - Completed 11 - Incomplete 12 - Skipped The state is available through a property called "TaskStateID". I can do this in LINQ with just one state as shown here: var filteredTasks = from task in tasks select task; // Do stuff with filtered tasks string selectedComboBoxValue = GetFilterComboBoxValue(); if (selected ComboBoxValue == 3) { filteredTasks = filteredTasks.Where(p => p.TaskStateID == 10); // How do I use an 'OR' here to say p.TaskStateID == 10 OR p.TaskStateID == 11 OR p.TaskStateID == 12 } As shown in the comment above, how do I use an 'OR' in a LINQ statement to say p.TaskStateID == 10 OR p.TaskStateID == 11 OR p.TaskStateID == 12? Thank you

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• Using Linq on a Dataset

  - by JasonMHirst

  Can someone enlighthen me with regards to Linq please? I have a dataset that is populated via a SQL Stored Procedure, the format of which is below: Country | Brand | Variant | 2004 | 2005 | 2006 | 2007 | 2008 The number of rows varies between 50 and several thousand. What I'm trying to do is use Linq to interrogate the dataset (there will be several Linq queries based on user options), but a simple example would be to SUM the year columns based on Brand. I have the following that I believe creates a template for me to work with: But from here on I'm absolutely stuck! sqlDA.Fill(ds, "Profiler") Dim brandsQuery = From cust In ds.Tables(0).AsEnumerable() Select _BrandName = cust.Item("BrandName"), _y0 = cust.Item("1999"), _y1 = cust.Item("2004"), _y2 = cust.Item("2005"), _y3 = cust.Item("2006"), _y4 = cust.Item("2007"), _y5 = cust.Item("2008") I'm tried to look at examples, but can't see any that are VB.Net based and/or show me how to Sum/Group. Can someone please provide an example so I can perhaps learn from it. Thanks.

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• Simplest LINQ in C# troubleshooting.

  - by Jay

  I'm trying to learn a bit of LINQ but I'm having compile issues right off the bat. Is there any specific reason why this won't work? using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace HelloLINQ { class HelloLINQ { public static void Main() { Example1(); } public static void Example1() { var numbers = new int[] { 1, 5, 3, 7, 3, 8, 9, 3, 6, 6, 2 }; var under5 = from n in numbers select n; foreach (var n in under5) { Console.WriteLine(n); } } } } The error is: Could not find an implementation of the query pattern for source type 'int[]'. 'Select' not found. Are you missing a reference to 'System.Core.dll' or a using directive for 'System.Linq'?

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• Linq-to-SQL and Performance.

  - by jalpesh

  HI, I am developing asp.net mvc site with linq-to-sql we are having 1000 cocurrent users and we are having performance problems. I have found that stackovewflow is also build on linq-to-sql? So can anybody know how they improved performance. Without line performance was good each page are loaded in 3 seconds but after migrating to linq as per our client requirement page comes in 8 to 10 seconds which is not acceptable performance. Our HTML is very clear but we are having very complex database operations. Any tip or code will be best answer. Thanks in advance,

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• How do I generate optimized SQL with my (added) partial methods on LINQ entities

  - by Ra

  Let's say I have a Person table with a FirstName and LastName column. I extended the Person LINQ entity class with a get property "FullName", that concatenates the first and last names. A LINQ query like: from person... select fullName where id = x generates SQL selecting all Patient columns, since FullName is evaluated after firing the query. I would like to limit the select clause to only the 2 columns required. This is a simple example, but the limitation it shows is that I cannot isolate my business/formatting rules but have to embed them in the LINQ query, so they're not reusable (since it is in the select part) or I need select both columns separately, and then concatenate them higher up in the data or business layer with static helper methods. Any ideas for a clean design using the entity partial classes or extensions? Thanks

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• Translate SQL to LINQ query - group/join/filter

  - by Paddy

  I have the following query: SELECT S.[FlowOrder], S.[DESCRIPTION], COUNT(I.ID) FROM WorkFlowStatus AS S INNER JOIN Item AS I ON S.ID = I.StatusID WHERE I.Installation = '1' GROUP BY S.[Description], S.[FlowOrder] ORDER BY S.[FlowOrder] Which gives me the count of an item, grouped by a foreign key to workflow, outputting the descriptive name from my FK table. I've go this far with the LINQ query (using LINQ-to-SQL) in the background: var items = from s in _entities.WorkflowStatus join i in _entities.Items on s.ID equals i.StatusId into Statuses orderby s.FlowOrder select new {s.Description, ItemCount = Statuses.Count() }; How do I get the where clause in the SQL into this LINQ query?

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• linq with Include and criteria

  - by JMarsch

  How would I translate this into LINQ? Say I have A parent table (Say, customers), and child (addresses). I want to return all of the Parents who have addresses in California, and just the california address. (but I want to do it in LINQ and get an object graph of Entity objects) Here's the old fashioned way: SELECT c.blah, a.blah FROM Customer c INNER JOIN Address a on c.CustomerId = a.CustomerId where a.State = 'CA' The problem I'm having with LINQ is that i need an object graph of concrete Entity types (and it can't be lazy loaded. Here's what I've tried so far: // this one doesn't filter the addresses -- I get the right customers, but I get all of their addresses, and not just the CA address object. from c in Customer.Include(c = c.Addresses) where c.Addresses.Any(a = a.State == "CA") select c // this one seems to work, but the Addresses collection on Customers is always null from c in Customer.Include(c = c.Addresses) from a in c.Addresses where a.State == "CA" select c; Any ideas?

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• SCOM, Server 2008 and SQL Server 2008

  - by Jacques

  Hi there, I'm trying to setup SCOM(System Center Operations Manager 2007 (SCOM) – Platform Monitoring) on my Server 2008 machine using SQL Server 2008 running on the same machine. When I check my prerequisites I get problem on SQL and Active Directory components. (I'm running SQL server 2008 and Server 2008 with active directory not installed) Errors: 1.Microsoft SQL Server 2005 Service Pack 1 required. Details: SQL Server 2005 SP1 is the next version of SQL Server. SQL Server 2005 Enterprise Edition, is a complete data and analysis platform for large mission-critical business applications. The link provided in the resolution column is a trial version of the product and is not supported by the Microsoft SQL Server team In order to install active directory needs to be present. Details:Setup failed to verify the presence of Active Directory for this server. I've got a couple of questions I need answering, hope someone can help. Do I need to install Active Directory for SCOM to work? Can I run SCOM with an SQL 2008 Database? How do I get pass these problems?

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• Is the master database backup crucial for restoring MS SQL server in the event where you have to res

  - by Imagineer

  I have been advise by Commvault partner support to turn off the backup of the master database as the backup failed due to the log file being lock. The following is the advise given: "The message is caused by Commvault’s inability to backup the master database’s transaction log. If this is happening intermittently its possible that something is locking the transaction log, preventing SQL iData agent from accessing the log. Typically the master database is just a template and is not used by any applications (applications that do require the use of an SQL database create their own) so there should be no harm in preventing it from being backed up You can do this by nominating NOT to back it up in the primary copy for the SQL data agent" The following is the error that I get. sqlxx SQL Server/ SQLxx N/A/ System DBs 19856* (CWE) Transaction Log N/A 01/08/2010 19:00:16 (01/08/2010 19:00:18 ) 01/08/2010 19:03:15 (01/08/2010 19:03:14 ) 1.44 MB 0:01:11 0.071 2 0 1 ITD014L2 Failure Reason: • ERROR CODE [30:325]: Error encountered during backup. Error: [ERROR: [Microsoft][ODBC SQL Server Driver][SQL Server]Cannot back up the log of the master database. Use BACKUP DATABASE instead. [Microsoft][ODBC SQL Server Driver][SQL Server]BACKUP LOG is terminating abnormally.] Job Options:Create new index, Start new media, Backup all subclients, Truncation Log, Follow mount points , Backup files protected by system file protection , Stop DHCP service when backing up system state data, Stop WINS service when backing up system state data Associated Events: • 79714 [backupxx/JobManager] [01/08/2010 19:03:15 ]: Backup job [19856] completed. Client [sqlxx], Agent Type [SQL Server], Subclient [System DBs], Backup Level [Transaction Log], Objects [2], Failed [1], Duration [00:02:59], Total Size [1.44 MB], Media or Mount Path Used [ITD014L2]. • 79712 [sqlxx/SQLiDA] [01/08/2010 19:01:53 ]: Error encountered during backup. Error: [ERROR: [Microsoft][ODBC SQL Server Driver][SQL Server]Cannot back up the log of the master database. Use BACKUP DATABASE instead. [Microsoft][ODBC SQL Server Driver][SQL Server]BACKUP LOG is terminating abnormally.] • 79711 [sqlxx/SQLiDA] [01/08/2010 19:01:51 ]: Query Result [[Microsoft][ODBC SQL Server Driver][SQL Server]Cannot back up the log of the master database. Use BACKUP DATABASE instead. [Microsoft][ODBC SQL Server Driver][SQL Server]BACKUP LOG is terminating abnormally.]. • 79707 [backupxx/JobManager] [01/08/2010 19:00:15 ]: New backup request received for Client [sqlxx], iDataAgent [SQL Server], Instance [SQLxx], Subclient [System DBs], Backup Level [Transaction Log]. Files failed to back up: • Backup Database[master] Failed Please advise, thank you.

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